Why terrorist attacks London, Paris ...?

SKUM

Because it was the British Empire and French Empire that invaded & pillaged their land in the late 1800's & early 1900's, Franky....Now they have "grown up" as nations, have the same weapons you do, and the same access to History that you do (though apparently you haven't bothered to look at it!)...

What would YOUR reaction be if you were living in a tent or a cave with next to nothing, and discovered it was because the French & British (and Germans, & Belgians) had robbed YOUR ancestors blind, and that was in large part why your life today totally sucked?

I seem to recall terrorist bombs going off in New York and Boston, just to name two.

They're perceived centers of western power and easier to reach then the U.S.

They are part of a coalition against ISIS

Because contrary to a popular belief seemingly perpetuated by American schools and media... the USA is not the only country in the world that has offended other nations..

France has a complicated history with Islam going back to the middle ages...and their colonial history bred more than a few lingering resentments (anybody remember Viet Nam?). They have had troops in Mali the past several years battling insurgents and making enemies among radical Islamists far beyond the region.

England is still blamed for the meddling in and partitioning of the Middle East that resulted in the state of Israel...and again, resentment there go back centuries before the USA ever existed..More recently, they are seen as an equal offender with the USA in the Gulf Wars.

Ultimately though, the attacks simply expose the myth that Islamic radicals simply want to be "left alone"... As with radicals of all ilks, the existence of anything that goes against their rigid core of beliefs ANYWHERE is considered a threat....so it must be attacked, destabilized and made to fail by any means in order to prove the "superiority" of those that survive..

They like French fries.

Because those who orchestrate these attacks hate freedom.
https://www.youtube.com/watch?v=C-qoU_nOzTs
https://www.youtube.com/watch?v=kqwhb6KfdfM
https://www.youtube.com/watch?v=SdqBee3M-Xc

They would get more attention.